The present invention relates to a fastening system for pull type swage fasteners including a pin and a collar with the collar adapted to be swaged into the pin with a mandrel removably secured in the shank of the pin and adapted to be gripped by an installation tool for applying the required relative axial pulling force between the pin and collar for swaging the collar.
The present invention relates to two-piece swage type fasteners or lockbolts generally of the type illustrated in U.S. Pat. No. 2,531,048 to L. Huck, issued Nov. 21, 1950, and U.S. Pat. No. 3,215,024 to Brilmyer et al issued Nov. 2, 1965; there are numerous other variations of swage type fasteners such as U.S. Pat. No. 3,915,053 to J. Ruhl, issued Oct. 28, 1975, U.S. Pat. No. 4,472,096 to J. Ruhl and R. Dixon, issued on Sep. 18, 1984 and U.S. Pat. No. 5,090,852 to R. Dixon, issued Feb. 25, 1992.
A typical swage type fastener includes a pin and a collar with the pin shank having a locking portion with lock grooves and, with the pull type, the pin shank terminating with a pull portion with pull grooves. The pull grooves are adapted to be gripped by matching teeth in chuck jaws of an installation tool having a swage anvil adapted to engage the collar whereby a relative axial force can be applied between the pin and collar to secure workpieces together under a preselected clamp force. As the relative axial force increases to provide the desired clamp force the installation is completed as a magnitude of relative axial force is attained to move the anvil over the collar to swage it into the lock grooves. Here the relative axial force is a tensile load on the pin via the chuck jaws and a compressive load on the collar via the tool swage anvil.
In pull type swage fasteners the pull portion typically is connected to the lock groove portion by a breakneck groove of reduced strength which is adapted to fracture at a preselected magnitude of axial or tensile force greater than that required to swage the collar whereby the pull portion, or pintail, will be severed from the pin shank and discarded after completion of swaging. See the patents cited above.
In addition with fasteners including pins having the pull grooves on a severable pintail the breakneck groove must also be of sufficient strength to withstand the high tensile load for swaging and the pull grooves must be similarly of sufficient strength to accept the relative axial pull load applied by the engaged teeth of chuck jaws on the installation tool. This routinely requires that the pull portion be of a relatively large diameter so as to have sufficient material to provide the necessary size and strength for the breakneck groove and also to inhibit fracturing of the pull grooves instead of the breakneck groove. In aerospace applications, the fasteners are most frequently made of a lightweight, high strength material which can be somewhat costly. Thus the severable pintail adds to the overall cost of each fastener. Certain systems have been developed for pull type swage type fasteners in which the pin is gripped externally and/or internally by a threaded member of the installation tool. Such systems are shown in U.S. Pat. No. 5,315,755 to Fulbright et al issued May 31, 1994 and U.S. Pat. No. 6,233,802 to Fulbright issued May 22, 2001.